It is common in the electronic arts to use reference voltages in connection with complex circuits and systems. Various circuits for generating reference voltages are well known, including those which employ temperature compensation so that the reference voltage is substantially independent of temperature over a significant range. It is also known to use cascaded voltage reference circuits.
However, these prior art circuits suffer from a number of limitations and disadvantages. For example, the ripple rejection is often not as large as is desired. Also, many prior art voltage reference circuits are very complex and occupy larger circuit area than is desired. These problems are exacerbated when it is desired that the reference voltage be small, e.g., close to the semiconductor band-gap voltage Vbg (Vbg for silicon=1.22 volts at zero Kelvin).
Accordingly, there is an ongoing need to have voltage reference circuits which overcome these and other deficiencies well known in the art, especially, circuits which provide improved ripple rejection while occupying comparatively small chip area.